In Bilbao, an industrial city in the Basque region of Spain, the outline of the SAN Mames Stadium has quietly changed with an architectural revolution. Athletic Bilbao has draped a light “ETFE membrane armor” over this century-old home ground.
The morphological metaphor of the rebirth of the lion’s nest
The ETFE membrane structure design of SAN Mames Stadium subtly echoes the team’s culture. The nickname of Athletic Bilbao, “Lion”, has been transformed into architectural language – the membrane surfaces on the east and west sides undulate in a wavy pattern, simulating the dynamic curves of a lion’s mane. The highest point reaches 42 meters and the lowest point 28 meters, creating a highly tense visual impact. The total area of the membrane structure is approximately 12,000 square meters, composed of 180 diamond-shaped ETFE air pillow units. The aluminum alloy frame at the edge of each air pillow is treated with the traditional forging process of the Basque country, presenting a rough texture of metal and creating a spiritual resonance with the team’s tough playing style.
This form design is not merely an aesthetic expression. The slope of the inclined membrane surface has been optimized through wind tunnel tests, which can guide the common westerly wind in Bilbao to the area below the grandstand, forming a natural ventilation system that can replace the air three times per hour. The hyperbolic shape of the membrane surface enables rainwater to flow along the preset trajectory to the drainage channels on both sides, increasing the drainage efficiency by 40% compared to the traditional flat roof structure. This ensures that there is no water accumulation problem in the stadium during heavy rain, allowing the “rain game” to no longer affect the viewing experience of fans.
Practical wisdom awaiting response
The rainy and foggy maritime climate of the Basque region makes the functional design of ETFE membrane structures particularly crucial. In the selected double-layer ETFE air pillow, the inner membrane is printed with gray dots of gradually changing density, which can filter 35% of ultraviolet rays while retaining 75% of visible light transmittance. This “intelligent dimming” effect enables the grandstand area to avoid glare interference on sunny days and introduce sufficient natural light on cloudy days, reducing the energy consumption of artificial lighting. The acoustic properties of membrane materials have also been precisely utilized. The connection node between the ETFE membrane and the steel structure adopts an elastic damping design, which can absorb 20% of the environmental noise. This not only reduces the interference of traffic noise outside the stadium to the game but also enhances the concentration effect of the fans’ cheering inside the stadium. As a result, the sound pressure level of the “Lion’s Nest” can reach up to 110 decibels, creating a terrifying home atmosphere for the opponents.
Innovations in the details of fan experience
The ETFE membrane structure brings an all-round upgrade of the viewing experience to the SAN Mames Stadium. The column-free design of the east and west stands (with a maximum span of 56 meters) combined with the high light transmittance of the membrane material enables 90% of the spectator seats to enjoy unobstructed views. Even those sitting in the back rows can clearly capture the details of the field.
The technological inheritance of traditional industries
Bilbao, as a major center of the steel industry, has always had its architecture carry an industrial gene. The connection nodes between the membrane material and the steel structure adopt the traditional “fishbone” mortise and tenon design of the Basque country, which not only ensures the structural strength but also continues the regional craftsmanship characteristics. It is not only the material carrier of the team’s spirit, but also a vivid portrayal of the Basque region’s “industrial tradition + modern technology” – just like Athletic Bilbao’s persistence and innovation, it is always full of vitality on the football field.
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